Intercommunicating system and apparatus therefor



June 28, 1938. L. w. PARKER INTERCOMMUNICATING SYSTEM AND APPARATUS THEREFOR Filed April 26, 1957 3 Sheets-Sheet l INVENTOR ATTORN EY June 28, 1938. L. w. PARKER 2,121,333

INTERCOMMUNICATING SYSTEM AND APPARATUS THEREFOR Filed April 26. 1937 :s SheetsSheet 2 INVENTOR Y% ATTORNEY June 28, 1938. w PARKER 2,121,883

INTERCOMMUNICATING SYSTEM AND APPARATUS THEREFOR Filed April 26, 1937 5 Sheets-Sheet s z .z r 57 1 3 3 a mv v n ag ng any; 1 n vg v 25 7 ,25 23 I n I "l 5 /9 A L INVENTOR ATTORN EY Patented June 28, 1938 UNITED STATES INTERCOMMUNICATING SYSTEM AND AP- PARATUS THEREFOR Louis W. Parker, Astoria, N. Y., assignor to S. M.

Saltzman, New York, N. Y.

Application April 26, 1937, SerlalNo. 138,894 I 19 Claims.

This invention relates to intercommunicating systems, and with particularity to two-way intertcommunicating systems of the central station A principal object of the invention is to provide an intercommunicating system which is particularly well suited for use on craft of all kinds such as ships, railway trains and the like.

Another principal object is to provide an intercommunicating system of the central station type with a plurality of outlying stations equipped with loud-speaking signal reproducers so coupled to the transmission line that maximum of safety and reliability in signal communication is attained.

Another object is to provide an improved method and means for coupling a plurality of signal reproducing devices such as loud-speakers or the like, to a transmission line whereby failure or abnormal conditions in one reproducer are of negligible effect on the other reproducers.

A further object is to provide a telephone intercommunicating system which is intended for use in situations where the extraneous noise level is very high, and wherein the telephone transmission line is required to carry audio frequency currents of large power amplitude.

A still further object is to provide an improved method and apparatus for controlling a signal call device ina telephone intercommunicating system. i v

A feature of the invention relates to the means for inductively couplinga loud-speaking signal reproducer or similar device, to asubstantially linear shielded cable whereby increased coupling efficiency is attained.

Another feature relates to the means for inductively coupling a signal device to a telephone wire without breaking the wire and with a high degree of coupling efiiciency.

Another feature relates to an improved circuit the relay is designed so that itscontacts remain contacts only after a normally closed shunt around the relay is removed and during the interval the current through the relay is dropping to itsnormal steady state.

A still further feature relates to the novel organization, arrangement and relative connection of parts which go to make up a safe, reliable and efiicient two-way intercommunicating system peculiarly well adapted for use on ships and other locations having a high extraneous noise level.

Other features and advantages not specifically enumerated will be apparent after a consideration of the following detailed descriptions and the appended claims.

While certain aspects of the invention will be described as embodied in a communicating system of one particular type, it will be understood that this is done 'merely for explanatory purposes and not by way of limitation. Furthermore only'those parts of the apparatus and system will be described as are necessary to a complete understanding of the various features. Accordingly in the drawings Fig. 1 is a schematic perspective view of the coupling arrangement according to the invention.

Fig. 1a is a modification of the split-sheath cable of Fig. 1.

) Fig. 2 is a schematic wiring diagram of a system embodying the principle of Fig. 1.

Fig. 3 is a detailed schematic wiring diagram of a preferred form of pilot or loud-speaker control circuit.

Fig. 4 is a schematic layout showing one typical use of the invention aboard a ship.

' Fig. 5 is a schematic wiring diagram of part of the system shown in Fig. 4, and embodying the principles of the preceding figures.

In certain types and locations of signal intercommunicating sy'stems it is important that the signals bereproduced with sufiicient volume as to be clearly distinguishable even in extremely and individual amplifiers at each of the receiving points. Apart from the cost of such arrangements is the difficulty that in certain receiving locations it is not advisable or convenient to have local power supplies. Thus aboard a ship it is highly desirable to have a central source of electric power and to avoid the use of separate power lines (as distinguished from signal lines), to each receiving point. Accordingly the present invention is concerned mainly, although not entirely, with a signal intercommunicating system where the signal energy is amplified to the requisite level at the central point and is transmitted at this high level to the several receiving points. Because of the heavy signal power carried by the line, it is important where a plurality of signal reproducers are coupled to the line, that abnormal conditions or undesirable interference at one reproducer, have substantially negligible effect on the other reproducers. While various proposals have heretofore been made whereby signaling devices can be coupled to a telephone line or to a cable, these prior proposals have involved a physical or conductive connection to the wire or have required high amplification of the picked up signals in order to operate a loudspeaker or the like. These prior arrangements have been wholly useless where the line is in the form of a shielded or armored cable. I have found that it is possible to couple a plurality of signal devices to a shielded cable by using the shield to complete an inductive loop to act as the primary of a pick-up transformer which may be connected directly to a loud-speaking device or the like. Such an arrangement is schematically illustrated in Fig. 1 wherein a section of an armored cable carrying audio frequency currents, is shown. The numeral I represents a wire of the cable which is provided in the usual manner with aninsulating covering 2 of any well-known material, and also with any well known form of metal sheath 3. This metal sheath may consist of an under layer of a metal wrapping overlaid with a continuous lead covering. As will be described in detail hereinbelow, the wire I and the sheath 3 form the conductors of a telephone or signaling pair, the current flowing through the wire I in the opposite direction to the flow through the sheath as indicated by the arrows. Ordinarily the sheath being parallel to and completely enclosing the wire, the resultant electromagnetic field would be substantially negligible so that a pick-up coil surrounding the cable would have substantially negligible signal voltage induced therein, and certainly not enough to operate a device such as a loudspeaker. However if the sheath is broken so as to produce a gap as indicated in Fig. 1 by the numerals 5 and 6, and the ends 5, 6 are connected by a wire loop 4, then this loop 4 together with the section of wire I between points 5 and 6, constitutes a complete inductive loop. Consequently if a suitable pick-up coil is located properly with respect to this complete loop, a substantial signal voltage will be induced therein. While the invention is not'limited to any particular form of pick-up coil, it is preferred to employ a coil comprising a split magnetic core as shown, comprisingtwo abutting laminated sections 1, B to act as a closed transformer core, it being understood that a suitable casing may be provided for the core when the sections are placed together and fastened in any suitable manner. A transformer secondary winding 8 of any desired number of turns is insulatingly wound around one leg of the core.

The terminals II), II of this secondary winding may lead directly to any suitable form of signal reproducer, for example an electric loudspeaker or the like. While Fig. 1 shows the sheath removed from a considerable length of the cable, it will be understood that this is not necessary so long as the sheath current is compelled in whole or in part to flow through the conductor 4. Thus as shown diagrammatically in Fig. 1a the sheath 3 is removed in a very narrow band, as for example by a special saw, and the resultant annular gap may then be filled or impregnated with a suitable insulating material to prevent direct contact with the wire I.

With-the foregoing arrangement I have found it possible by impressing the audio frequency currents on the wire I and sheath 3 at high current density, to produce at the terminals I0, II sufficient signal voltage to operate a loudspeaker directly, i. e., without any local amplification between the pick-up coil and the loudspeaker.

Referring to Fig. 2, there is shown in generalized form a system employing a plurality of loudspeakers located at a plurality of receiving points supplied by a common cable. Thus a source of audio frequency waves I2 at a central station impresses thesignal currents by means of a coupling transformer I3, on the cable wire I and the sheath 3. If desired, a key I4a may be provided to control the continuity of the line for purposes described hereinbelow. As indicated, the outer metal cable sheath is broken where it passes the receiving points or stations I4, l5, l6 and surrounding the gapat each station is a pick-up transformer I! having a secondary winding similar to that of Fig. 1. The gaps in the sheath are bridged by conductors 4 to complete the primary inductive loops of the respective transformers. At the terminal of the cable the sheath 3 is connected by a wire I8 to the wire I thus completing the signaling circuit, and if desired this terminal of the circuit may be grounded as shown. The terminals I0, II of each transformer are connected to the winding II! of a suitable form of loudspeaker 20.

In certain cases it may be desirable to have one or more loudspeakers normally disconnected from the cable except when signals are to be sent thereto. This may be rendered necessary where the loudspeaker is located in a place where it is likely to pick-up as a. microphone, local interfering noises. Such an arrangement is illustrated in Fig. 3, wherein one of the stations of Fig. 2, for example station I4, is shown in schematic detail. The pick-up transformer I I instead of being provided with a single secondary winding is provided with two secondary windings 2I, 22. Winding 2I is preferably of high impedance and large number of ampere-turns, while winding 22 is preferably of low impedance and small number of ampere-turns. There are provided a pair of contacts 23 through which the loudspeaker winding I9 is connected to the winding 22, these contacts being controlled by a relay winding 24. For the purpose of energizing winding 24, it is connected in circuit with winding 2| through a low or audio frequency choke coil 25a, to a full-wave rectifier arrangement 26a, preferably of the dry or copper oxide type. The rectified output therefore controls the contacts 23, and when the powerful signal currents are not impressed on the cable wire and sheath, the contacts 23 are open and loudspeaker 20 is ineffective. When the signal cur- 76 rents of suflicient power are impressed on the line, contacts 23 close and connect the loudspeaker in circuit. Instead of using the audio frequency signal currents themselves to control contacts 23, these signal currents may be superposed on a low frequency current, for example a 60 cycle alternating current, which latter is practically inaudible in the loudspeaker. The existence of this 60 'cycle current on the line maintains contacts 23 closed. If for any reason contacts 23 should stick when not desired,,there will be only a slight increase in the noise level caused by device 20 acting as a microphone, because of the low impedance of winding 22.

Fig. 4 shows a typical arrangement on board a ship, embodying the principles already described. The numeral 25 represents acentrai source of power supply, and numeral 26 represents the bridge or other central point of communication. The loudspeakers are arranged so that some are equipped with pilot circuits as disclosed in Fig. 3, while others'are coupled to the cable as described in connection with Figs. 1 and 2. The former are represented in Fig. 4 by the circles 2i, and the latter by the rectangles 25. The loops joining the gaps in the cable sheath corresponding to the loops of Fig. l, are indicated by the numeral 29, while conductors fill, 30 represent the metal sheath of the cable and the cable wire respectively.

While any well known calling, supervisory andswitching circuit may be utilized in the system of Fig. 4., it is preferred to employ an arrangement such as shown in Fig. 5. Merely for purposes of explanation it will be assumed that the loudspeaker 26c alone is to be used for two-way communication, while the remaining loudspeakers are to be used for incoming messages only, as indicated by the contacts 23 corresponding to contacts 23 of Fig. 3. The control panel for the system is indicated by the dotted rectangle 32 and may be located at the bridge 26, while the remaining parts, except of course the cable and its coupled loudspeakers, are located at the central power room 25. The signaling line circuit comprising the cable sheath and the cable wire, is controlled by relays 33, 34. Relay 34 is provided with an armature 35 and a pair of contacts 36, 31 whichselectively-connect either the incoming signal amplifier 38, or the outgoing signal amplifier 39, to the line. There is also provided a source 46 of low frequency alternating current, for example 66 cycles, which is applied to the line to control the contacts 23 as tacts 43, 44 of relay 45. The source 42 may be a 24 volt rectified and filtered power supply, one terminal of which is grounded as shown. The relays 33, 34 and 45 are designed to operate from a 24 volt source but may operate from a sourceas low as 8 volts and as high as 48 volts. For the purpose of controlling the various amplifiers and the light 4|, there is provided a switch having two fixed contacts 46, 41 and a switch arm 48. Contact 41 is grounded; contact 46 is connected to one terminal of the winding of relay 33, the other terminal of which is grounded; and the switch arm 48 is connected through the winding of relay 34 to the positive terminal of source 42. vA microphone 43 and a loudspeaker 50 are also provided at a convenient point. The continuity of the line at the far tercable wire.

'33 to ground.

' from a distant loudspeaker, for example loudspeaker 2||e acting as a microphone, these currents'flow through the cable wire, condenser 53, contacts 54, 55, contacts 35, 36, primary winding 56 of input transformer 51, returning thence by conductor 58 to the sheath 3, switch 5| to the The secondary winding 59 is connected to the input of a suitable audio frequency amplifier 3B the-output of which is applied to loudspeaker 56. Thus the messages may be transmitted through loudspeaker Me to loudspeaker 50.

The foregoing signaling circuit is complete if the person at the bridge has operated or left key 48 in its In position. If the switch is in its -Ofl position when communication is desired with the bridge, then under these conditions a circuit exists from the positive terminal of source 42, coil 34, switch 48, contact 46, winding of relay Relay 33 thus stays operated and breaks the line circuit at contacts 54, 55. The operation of relay 33 also removes the shunt from the winding of relay 45, at contacts 60, hi. While there existed previouslly a circuit from the positive terminal of source 42, resistance 62, iron core choke coil 63, winding of relay 45, cable wire I, switch 5| to ground, the relay 45 did not operate because of the shunt through contacts 6|, 62. Relay 45 is a marginal relay and will not normally operate by the steady state current which flows from source 42 in series With elements 62, 63 and winding of relay 45. However the instant the shunt is removed at contacts 66, 6i, the line current does not drop to its lower steady" state value by inclusion of the winding of relay 45 in the circuit, since the choke coil 63 acts as an electrical inertia or storage device. In other words there is an appreciable interval of time required for the line current to drop from its value with elements 62, 63 only in circuit, to its value with elements 62, 63 and 45 in circuit and during this interval the current is of sumcient magnitude to operate said relay 45. It will also be understood that relay 45 when operated is held operated by the final steady state current.

As long as relay 45 is operated, the circuit for lamp 4| is broken and this lamp is unlighted. When the person at loudspeaker 20c wishes to attract the attention of the person at the bridge, the former momentarily opens switch 5|, whereby relay 45 is immediately deenergized and remains released, thus closing the circuit for lamp 4| The person at the bridge noticing the lighted lamp, operates switch 48 to either the In or the Out position. In the former position relay 33 releases to complete the talking circuit from the loudspeaker 20c through contacts 54, and contacts 35, 36, to the incoming signal amplifier 38 and the loudspeaker 50. In the latter position, relay 34 is operated thus completing the talking circuit from loudspeaker 20c to the outgoing signal amplifier 39 and the microphone 49. It should be noted that with respect to relay 45 and relay 33, that the contacts 60, 6| open to remove the shunt around relay 45, slightly in advance of the opening of contacts 54, 55.

Should switch 48 be in its In position and this fact is not apparent to the person of loudspeaker Me, the switch 5| may be operated momentarily resulting in a click in the loud speaker 2Ile each time the switch 5i opens and closes the circuit. Should by chance the switch 5| get out of order; the condenser 52 provides a path for the audio-frequency currents. Likewise should the contacts of relay 33 get out or order, condenser 53 maintains the A. C. circuit. During any of these latter abnormal conditions, lamp 4| stays lighted as an indication of trouble.

While specific apparatus and circuits have been described herein, it will be understood that the invention is not necessarily limited thereto. For example the switching, supervisory and marginal relay arrangements of Fig. 5 are applicable to any type oi signaling line and are not necessarily limited to a line wherein the cable sheath acts as a line conductor. Likewise while the inven-- tion has been described in connection with a system of telephone communication, it will be understood that it is also applicable to telegraphic communication and the like. Various changes and modifications may be made in the disclosure without departing from the spirit and scope of the invention.

What I claim is:

l. A signaling system including a marginal relay, a source of steady D. C. potential in circuit with the winding of said relay, another relay for controlling a shunt around the winding of the marginal relay, and means efiective when said shunt is removed to provide a time interval before the current through said winding drops to its steady state value, and means to supply said marginal relay with current during said interval to operate said relay only during said interval, said relay remaining released when 0riginally energized by current of the steady state value.

2. A signaling system including a signaling line, a pair of stations between which said line extends, a signal call device at one of said stations, a marginal relay to control said device,'

another relay controlling said marginal relay by controlling a shunt around the winding of said marginal relay, and means including a source of current and an electrical energy storing device in circuit with the winding of the marginal relay to cause the marginal relay to operate its contacts when said shunt is removed but only during the interval the current therethrough is maintained above its steady state value by said storing means, said steady state current maintaining the marginal relay locked after it has once operated.

3. A signaling system including a signaling line, a relay having a winding in said line, means to supply current to said winding, another relay for controlling a shunt around the winding of the first relay, an electromagnetic storing means in circuit with the winding of the first relay to maintain the current through said winding above its steady state value for a predetermined time interval after removal of said shunt, means selectivelyto operate the second relay, the first relay remaining released when originally energized by the normal steady state current therethrough but operating when said shunt is removed and through said coil is at a certain level, said coil maintaining the current through said winding above its steady state value for a predetermined time interval subsequent to removal of said shunt to operate said relay only during said time interval, said relay remaining locked by said steady state current once it is energized but remaining released when originally energized by current of said steady state value. v

5. A signalling system comprising a signaling line including in series during communication the winding of a marginal relay, a low-frequency,

choke coil and a source 01' steady D. C. potential; another relay having contacts for placing a shunt around said winding and having contacts for opening and closing said line, said coil maintaining the current through said winding above its steady state value for a predetermined time interval subsequent to the removal of said shunt to operate said relay only during the said interval.

6. A signaling system including a first station, a second station, a. signaling line between said stations, a signal call device at one of said stations, a marginal relay having contacts to control the circuit of said call device to maintain said circuit open when communication is established between said stations, another relay having a pair of contacts to control the continuity of the signaling line and another pair of contacts to control a shunt around the winding of the marginal relay, a source of steady D. C. potential for operating said relays, an electric storing device in circuit with the winding of the marginal relay to maintain the current through said winding above its steady state value for a predetermined time interval subsequent to removal of said shunt, a multi-position switch at said one of said stations effective in one position to operate said other relay and to open said line, means at the other of said stations to break momentarily the circuit of the marginal relay to operate said signal call device, and circuit arrangements for maintaining said signal call device operated until said switch is moved from said one of said positions.

7. In a signaling system, a first station, a second station, a signaling line between said stations, a. signal call device at the first station, a marginal relay having a winding in said line and a contact to control the circuit of said device, said contact being operated to open said circuit when communication is established between said stations, 9. source of steady D. C. potential and a low-frequency choke coil connected to the winding of said marginal relay, another relay for controlling a shunt around the winding of the marginal relay, a signal transmitter and a signal reproducer at said first station, a multiposition switch eifective in one position to connect said transmitter to'said line and to maintain said shunt around the winding of the marginal relay, and effective in another position to connect said reproducer to said line while maintaining said shunt around said winding.

8. A. signaling system including a signaling line, a pair of stations between which said line extends, a signal transmitter, a signal reproducer, a. power amplifier for said transmitter, a power amplifier for said reproducer, means at the first station to indicate when the other station desires to establish communication therewith, a three-position switch effective in one position to connect the output of the transmitter to the line and in another position to connect the during which a current higher than the steady state current flows to operate said marginal relay.

10. In a signaling system a first station, a second station, a signaling line between said stations, a signal reproducer coupled to said line at said second station, a relay for controlling a local circuit for said reproducer, a signal reproducer at the first station, a signal transmitter at the first station, a source of pilot current,

means at the first station for applying said pilot current to said line to close the local circuit of the reproducer at the second station, and a multiposition switch at the first station for connecting the transmitter and reproducer at the first station selectively to said line.

11. In a signaling system, a central station, a signal call device at said station, a first outlying station, a second outlying station, each of said outlying stations arranged for two-way signal communication with the central station but only one of said outlying stations arranged tooperate said signal call device, a relay for,controlling the circuit 'of said call device, means at said one of said outlying stations for causing said relay to close the circuit of said deviceand to maintain it closed until the central station answers, a multi-position switch at the central station effective in one position to operate said relay to open the. circuit of said device and effective in another position to connect a signal transmitter at the central station to the line.

12. In a signaling system, a telephone line, a plurality of loudspeakers coupled to said line at a corresponding plurality of signaling points, a switch at one of said points for momentarily opening the line, a central station having a microphone and a loudspeaker, a supervisory lamp at the central station, a marginal relay controlling the lighting of said lamp, said relay remaining released when originally energized-only by the steady state current on the line but remaining locked by said steady state current after being energized by a higher value of line current, a multi-position switch at the central station effective in one position to maintain a shunt around the winding of said marginal relay and effective in another position to remove said shunt, said winding being connected in said line.

13. A system according to claim 12 in which the marginal relay is provided with an electromagnetic storing device to provide a delay in the dropping of the line current to its steady state in response to the removal of said shunt.

14. In a signaling system, the combination of a cable containing at least one insulated cable wire and having a conductive sheath, a signal reproducer, an electromagnetic loop for coupling the reproducer to the cable, said loop being constitute-d in part by a portion of the cable wire and in part by a conductor member connecting a gap in the cable sheath, another signal reproducer at a central station, a supervisory signal device at the central station, a relay at the central station for controlling said signal device, means associated with the first reproducer to cause said 'relay to close the circuit of said device, and circuit arrangements to cause said relay to maintain said device operated until the central station answers.

15. In a signaling system, a signaling line formed of a cable wire and a cable sheath, a plurality of loudspeakers each coupled to said line by a conductive loop formed in part by the cable wire and a conductive member bridging a gap in the cable sheath, a central station, means associated with one of said loudspeakers to operate a signal call device at said central station, means at said central station to establish communication with any of said loudspeakers, and means to impress a pilot current on said line to control the local circuits of said loudspeakers.

16. A system according to claim 15 in which the local circuit of each loudspeaker is provided with a relay and a rectifier controlled by said pilot current.

17. A system according to claim 15 in which said means associated with said one of said loudspeakers'includes a key for momentarily opening the line.

18. A system according to claim 15 in which all loudspeakers except said one of the loudspeakers is normally disconnected from the line and is connected thereto only in response to the application of said pilot current by the central station.

19. In combination a marginal relay having a contact to be operated, a line, a pair of contacts completing the line when closed and interposing thewinding of said relay in the line when open, said winding when interposed causing a reduction of the line current, a source of direct current, and electromagnetic means in circuit with Louis w. PARKER. 

